1. Field of the Invention
The present invention relates to an optical input device, and in particular, to a protective mechanism which detects whether a laser-emitting input device has been inverted during use.
2. Description of the Prior Art
A conventional optical mouse typically uses an optical detecting system to detect the movement of the mouse on a working surface, such that a cursor on a computer display can be controlled simultaneously. This type of technology is illustrated in U.S. Pat. Nos. 5,644,139 and 6,433,780, where an LED (light emitting diode) is adopted as a light source for detecting the movement of an optical mouse.
In order to overcome the divergence of the projected light from the LED, a so-called coherent light is introduced to the optical detecting system. An early example of such a laser optical detecting system for a computer mouse is disclosed in U.S. Pat. No. 4,794,384, in which the coherent light can be a laser beam or the like. U.S. Pat. No. 6,927,758 also discloses a dual lens laser detecting system for more accurate control of the movement of the cursor on the computer display.
Regardless of the type of laser or the type of laser detecting system used, there is still a possibility that the optical input device is inadvertently overturned (i.e., inverted) so that the laser beam is being emitted into the open work area occupied by the user. Even though the manufacturers of these existing optical input devices claim that the laser beam emitted from an inverted optical input device is harmless to the human eye, there is always a potential for harm. Thus, there remains a need to minimize harm arising from exposure to the laser beam from an optical input device.